Enhanced Oil Recovery (EOR) may be used to increase oil recovery in fields worldwide. There are three main types of EOR, thermal, chemical/polymer and gas injection, which may be used to increase oil recovery from a reservoir, beyond what can be achieved by conventional means—possibly extending the life of a field and boosting the oil recovery factor.
Thermal enhanced recovery works by adding heat to the reservoir. The most widely practiced form is a steam-drive, which reduces oil viscosity so that it can flow to the producing wells. Chemical flooding increases recovery by reducing the capillary forces that trap residual oil. Polymer flooding improves the sweep efficiency of injected water. Miscible injection works in a similar way to chemical flooding. By injecting a fluid that is miscible with the oil, trapped residual oil can be recovered.
Referring to FIG. 1, there is illustrated prior art system 100. System 100 includes underground formation 102, underground formation 104, underground formation 106, and underground formation 108. Production facility 110 is provided at the surface. Well 112 traverses formations 102 and 104, and has openings in formation 106. The portion of formation 106 is shown at 114. Oil and gas are produced from formation 106 through well 112, to production facility 110. Gas and liquid are separated from each other, gas is stored in gas storage 116 and liquid is stored in liquid storage 118.
U.S. Pat. No. 4,109,720 discloses that petroleum may be recovered from viscous petroleum-containing formations including tar sand deposits by injecting into the formation a solvent which is liquid at formation conditions and simultaneously therewith injecting a substance which will remain totally gaseous at the pressure and temperature conditions existing within the reservoir. The presence of noncondensible gas in the formation into which solvent is being injected prevents formation of a impermeable bitumen bank which blocks the further flow of fluids through the formation. The gas should be essentially unreactive with the solvent and formation fluids in order to obtain the desired benefits. Examples of suitable gases for the practice of this invention include methane, ethane, nitrogen, carbon dioxide, and mixtures thereof. U.S. Pat. No. 4,109,720 is herein incorporated by reference in its entirety.
There is a need in the art for improved systems and methods for enhanced oil recovery. There is a further need in the art for improved systems and methods for enhanced oil recovery using a solvent, for example through viscosity reduction, chemical effects, and miscible flooding. There is a further need in the art for improved systems and methods for solvent miscible flooding. There is a further need in the art for improved systems and methods for enhanced oil recovery with gravity drainage.